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Tensor products of operators—strong stability andp-hyponormality

Published online by Cambridge University Press:  08 November 2000

B. P. Duggal
Affiliation:
Department of Mathematics, Faculty of Science, University of Botswana, P/Bag 0022, Gaborone, Botswana, Southern Africa. E-mail: duggbp@noka.ub.bw
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Abstract

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We say that the operator T on a Hilbert space H into itself is strongly stable if \left\Vert T^nx\right\Vert →0 as n→∞, for allx∈H . If T is a contraction, then T is said to be cs-stable if T has C_0 completely non-unitary part. This note considers the strong stability of operators A⊗B and the p-hyponormality of operators A⊗B. It is shown that the contraction A⊗B is cs-stable if and only if so are the contractionscA and c^{−1}B for some scalar c andA⊗B is p-hyponormal if and only if A andB are. We also characterize p-hyponormal A⊗B for which the commutator |A⊗B|_{2p}−|A^*⊗B^*|^{2p} is compact.

Type
Research Article
Copyright
2000 Glasgow Mathematical Journal Trust